The present invention relates to a process for the work-up of polymer solutions comprising N-methyl-2-pyrrolidone and a polymer where the polymer solution is hydrogenated with hydrogen in the presence of a hydrogenation catalyst.
The present invention also relates to the product obtainable from said process, and to its use for producing, in particular, polyarylene ether products.
The present invention equally relates to a process for producing a polyarylene ether which comprises    (A) carrying out a polymerization reaction to produce the polyarylene ether    (B) removing inorganic constituents of the solution    (C) working the solution up in accordance with the process according to the invention    (D) producing polyarylene ether beads from the solution by separation into a precipitation bath, and    (E) extracting and drying the polyarylene ether beads.
The present invention also relates to the product obtainable from said process.
Polyarylene ethers, like polyarylene ether sulfones and polyarylene ether ketones, are, as is known to the person skilled in the art, high-performance thermoplastics, and feature high heat resistance, good mechanical properties, and inherent flame retardancy.
Polyarylene ethers, like polyarylene ether sulfones and polyarylene ether ketones, are often produced in solutions comprising N-methyl-2-pyrrolidone. N-Methyl-2-pyrrolidone (NMP) is a preferred solvent because its solvent properties permit very high polymer content in the polymer solution.
DE 195 01 063 discloses a process for the work-up of polyarylene ethers. The production of said polyarylene ethers is carried out for example in N-methylpyrrolidone in the presence of potassium carbonate. For the work-up the alkali metal halogenides formed during the reaction are removed from the reaction mixture, for example by means of filtration. Further work-up is carried out by precipitating the polyarylene ethers by adding of an aqueous base. By the process according to DE 195 01 063 polyarylene ethers with good properties are obtained. In terms of intrinsic color the polyarylene ethers according to DE 195 01 063 still show room for improvement.
DE 102 21 177 also discloses a process for the work-up of polyarylene ethers. For this the polyarylene ether solution is brought in contact with an adsorbent agent. In terms of intrinsic color the polymers according to DE 102 21 177 also still shows room for improvement.
An object was to provide a process which can produce polymers, in particular polyarylene ethers, and the resultant products from which have improved intrinsic color, increased soluble content, and improved melt stability value.
General information relating to the production of polyaryl ethers is found inter alia in R. N. Johnson et. al., and J. Polym. Sci. A-1 5 (1967) 2375, J. E. McGrath et. al., Polymer 25 (1984) 1827).
The person skilled in the art is aware of processes for producing polyarylene ether sulfones from aromatic bishalogen compounds and aromatic bisphenols or salts of these in the presence of at least one alkali metal carbonate or ammonium carbonate or alkali metal hydrogencarbonate or ammonium hydrogencarbonate, in an aprotic solvent, and these processes are known to the person skilled in the art, and are described in detail by way of example in U.S. Pat. No. 4,870,153, EP 113 112, EP-A 297 363, and EP-A 135 130, which at this point are expressly incorporated by way of reference. The following can in particular be found in those specifications by way of example: suitable starting materials, catalysts and solvents, suitable quantitative proportions of the substances involved, and suitable reaction times and suitable reaction parameters, such as reaction temperatures or reaction pressures, and also suitable work-up methods.
High-performance thermoplastics, such as polyaryl ethers, are produced by polycondensation reactions, where these are usually carried out at high reaction temperature in dipolar aprotic solvents, such as DMF, DMAc, sulfolane, DMSO, and NMP.
NMP is particularly preferred as solvent, because its good solvent properties also allow reactions to be carried out with very high polymer content. However, a disadvantage is the discoloration of the solvent during the condensation reaction, leading to ongoing discoloration of the polymer.